RADIOFREQUENCY ABLATION

Interview with Dr. Charles H. Koo, MD
Electrophysiology Department

Radiofrequency catheter ablation targets abnormal heart tissue responsible for rhythm disturbances using energy similar to that a surgeon uses to cauterize tissue. The most commonly used energy source is radiofrequency, but microwave, laser and freezing (cryo) are also used.

Dr. Charles T. Koo uses radiofrequency (RF) ablation to treat patients with a variety of tachycardias. He said RF energy is most commonly used in the procedure. Dr. Koo performs two to three ablations per week at Our Lady of Lourdes Medical Center in Camden.

According to Dr. Koo, RF ablation, which began to emerge in cardiac care in the 1970s, was developed more fully in the 1990s and today provides patients with tachycardias a high-success option with a low risk of complications. "Radiofrequency energy, a modified electrical impulse that converts electrical energy to heat, is used to ablate putative tissue responsible for arrhythmias," Dr. Koo said.

RF ablation is used to treat patients who have a variety of fast heart rhythms and who have failed conventional medical therapy. In 2004, the heart rhythms that are treated with RF ablation include SVT (supraventricular tachycardia), atrial fibrillation, atrial flutter, and ventricular tachycardia.

One advantage of RF ablation in treating complex heart rhythm disorders is that the procedure can be staged if necessary, although the associated risk factors must be evaluated. Dr. Koo said those factors are stroke, bleeding, heart attack and destruction of normal tissue.

In treating supraventricular tachycardia (SVT), RF ablation shows a >90 percent success rate, according to Dr. Koo. For ventricular tachycardia (VT) the rate is about 50 percent in the long term for patients who have had a heart attack and from 80 to 90 percent in patients with idiopathic VT. In younger patients with atrial fibrillation (AF), the success rate is 75 to 80 percent, but for older patients with chronic AF the success rate drops to 25 percent. "Currently, RF is not the first line therapies for such patients," Dr. Koo said.

Although the data have not yet been widely published, Dr. Koo said multiple trials now underway show promise for the use of RF ablation in the treatment of atrial fibrillation. "Catheter ablation for atrial fibrillation could be a development akin to stents for interventional cardiologists," Dr. Koo said. "We're not close to this, but if we were able to offer this even to a subset of patients, it would be tremendous."

Patients undergoing RF ablation are given a local anesthetic before one or more catheters are inserted in the groin, neck, elbow or under the collarbone. These together with x-ray are used to find the target for RF ablation. Once the electrophysiologist isolates the area of the heart causing the abnormal rhythm, a catheter with an electrode at the tip is inserted and positioned to come in contact with the abnormal tissue, which is then ablated. The procedure takes from two to four hours.

Meticulous mapping is necessary, Dr. Koo explained, to find the "critical portion of that heart rhythm and place a lesion in that area." The size of the targeted area is usually from 5 to 10 millimeters.

"There are several mapping systems. High-tech, high-end computers aid physicians in targeting the arrhythmias. Computerized mapping saves time, improves patient safety, cuts back radiation exposure and provides second-to-second documentation" of the heart rhythm. So thorough is the documentation that Dr. Koo compared it to "videotaping an operation."

"With today's technology you have a very good chance of offering a curative procedure. Ablation therapy has short-term risks but offers long-term benefits," Dr. Koo concluded.

In summary:

• Radiofrequency ablation is used to treat patients with a variety of tachycardias.
• If necessary, the procedure can be staged although associated risk factors must be evaluated.
• Trials now underway show promise for radiofrequency ablation as a treatment for atrial fibrillation.

A take-home message about…… Radiofrequency ablation

• Radiofrequency ablation shows a success rate >90 percent in treating supraventricular tachycardia (SVT).
• In patients with ventircular tachycardia (VT), the success rate is about 50 percent in persons who have had a heart attack, from 80 to 90 percent in those with idiopathic VT.
• The success rate in younger patients with atrial fibrillation (AF) is 75 to 80 percent, only 25 percent for older patients with chronic AF.